Fig. 6.

A An example MS/MS-HCD spectrum of a glycopeptide carrying a high-mannose type N-glycan, Man₅GlcNAc₂ on asparagine. It showed a series of glycan oxonium ions in the low mass region at m/z 163.0603, 204.0868, 366.1398, and 528.1929, respectively. A series of fragment ions due to neutral loss of the glycan moiety were observed as the main fragment ions in the HCD spectrum. Trace amounts of y-type and b-type peptide fragment ions were detected, confirming the sequence of the peptide backbone. B An example of MS/MS-ETD spectra from a glycopeptide carrying Man₅GlcNAc₂, showing fragment ions with minimal neutral loss of glycan moiety. All expected peptide c-type and z-type fragment ions were detected except c8 fragment ion, confirming the peptide sequence in high confidence as well as the site and mass of the glycosylation modification. An asterisk (*) represents carbamidomethylation of cysteine; at symbol (@) represents the site of N-glycosylation, respectively [55]